1. Field of the Invention
The present invention relates to the field of display, and in particular to a micro light-emitting diode (micro LED, μLED) display panel
2. The Related Arts
The panel display device, due to the advantages of high display quality, low power-consumption, thin size and wide application, is widely used in mobile phones, TV, PDA, digital camera, notebook PC, desktop PC, and so on, and becomes the mainstream technology.
The micro LED display device is a display device which utilizes high density micro-scaled LED array integrated on a substrate as display pixels to achieve image display. Similar to a larger-scaled outdoor LED display, each pixel is addressable and individually driven to emit light, and can be viewed as a reduce-sized outdoor LED display by reducing the inter-pixel distance from cm scale to mm scale. Micro LED display device and the organic light-emitting diode (OLED) are both self-luminous, but the micro LED shows the advantages of higher material stability, longer lifespan and no image imprinting as compared to the OLED, and is considered as the major competing technology for OLED display device.
Because of lattice match, micro LED element must be grown on a sapphire-based substrate by molecular beam epitaxy (MBE) method. To manufacture a display panel, the micro LED element must be transferred from the sapphire-based substrate to the receiving substrate for forming the display panel. The micro transfer printing (MTP) is a technology to transfer the micro LED element grown on the sapphire-based substrate to the receiving substrate. Specifically, a laser lift-off (LLO) technology is used to separate the micro LED bare chip from the sapphire-based substrate, and then a patterned polydimethylsiloxane (PDMS) transfer stamp is used to adsorb to the micro LED bare chip off from the sapphire-based substrate, the PDMS transfer stamp is aligned with the receiving substrate for positioning, and then the micro LED bare chip adsorbed by the PDMS transfer stamp is attached to the pre-set position on the receiving substrate, and then the PDMS transfer stamp is peeled off to accomplish micro LED bare chip transfer to form micro LED array substrate. Moreover, the receiving substrate is silicon substrate already prepared with circuit pattern, which may be rigid or flexible.
At present, the size of the sub-pixel in the flat panel display, such as, LCD panels is relatively large for the micro LED. If a micro LED is used to fill the position of the area equivalent of the existing sub-pixel area, a greater gap will appear between the sub-pixel areas, resulting in the screen door effect. In other words, the display will seem covered with a black mesh overlay on the image, similar to viewing through the screen door. To solve the screen door effect, an approach is to fill the area of the space equivalent to the existing sub-pixel with a plurality of micro LEDs. However, this approach requires a large number of micro LEDs, resulting in high costs.